Mesomorphic and dynamic properties of 3F5BFBiHex antiferroelectric liquid crystal as reflected by polarized optical microscopy, differential scanning calorimetry and broadband dielectric spectroscopy

This paper presents studies of the influence of various thermal treatments on molecular dynamics and phase behavior of 3F5BFBiHex antiferroelectric liquid crystal by a combination of polarized optical microscopy (POM), differential scanning calorimetry (DSC) and broadband dielectric spectroscopy (BDS). Three liquid crystalline phases: the paraelectric SmA*, ferroelectric SmC* and antiferroelectric SmC*A phases, and vitrification of SmC*A were found upon cooling. The cold crystallization of phase Cr was observed only upon heating at the rate lower than 1.5 K/min. During heating faster than 1.5 K/min 3F5BFBiHex shows the same phase sequence as on cooling. Two relaxation processes in the SmC*A phase obey the Vogel−Fulcher−Tammann (VFT) relation when approaching the glass transition temperature (Tg). An unusual finding that relaxation processes are preserved upon the SmC*A – Cr transition on heating is presented in detail. Finally, the time evolution of relaxation parameters during isothermal cold crystallization process in SmC*A is discussed.